1. Field of the Invention
The present invention relates generally to a brake for a motorized vehicle and more particularly to an airbrake which applies braking pressure to the driveline of a truck.
2. Discussion of the Background
Various kinds of automobiles use different types of braking systems in order to slow and stop the motor vehicle when desired. The most common type of brake utilizes an abrasive material in the form of a rotor and disc or shoe and drum whereby two parts of the brake are forced into engagement with the friction resulting between the abrasive surface and the other surface being used to slow the vehicle. The force which causes the two parts to come together may either be directly applied through a mechanical system or applied by way of a hydraulic system. Many trucks also used a compressed air system to add additional force to the braking engagement.
While many of these systems operate safely, there are often problems especially in larger vehicles, such as trucks, in terms of the braking distance necessary in order to stop the vehicle when fully loaded. In addition, when brakes are applied too quickly, it is possible for the truck to jackknife or skid. This is an especially dangerous situation when the truck is going downhill.
Other forms of braking are also known, such as electrical braking where the interaction of two electrical fields causes the driveline to be slowed. Also known are arrangements where a spring-mounted piston is pressed against by a cam arrangement on a shaft. One example of this type of arrangement is U.S. Pat. No. 2,880,825 which describes a brake having a piston exerting a frictional retarding force upon a cam. In particular, this arrangement includes a plurality of fluid pressed pistons arranged radially around a cam mounted on the shaft to be braked.
Other brakes are also known which utilize some form of cam arrangement in the application of the braking force. For example, U.S. Pat. No. 5,697,678 includes piston 16 and 17 driven by an eccentric shaft 15. U.S. Pat. No. 5,465,817 shows a hydraulic brake pump using an eccentric cam arrangement with pistons. Cams 34 mounted on shaft 36 drive pistons 46 within cylinders. U.S. Pat. No. 3,023,870 shows an auxiliary brake whereby the camshaft is movable by the depression of the brake pedal so that the pistons remain in the compression stroke and act as a braking device. U.S. Pat. No. 2,156,560 shows a similar compression brake system.
However, in all of these systems, optimal braking force is difficult to achieve and additional help in braking is always desirable in a fully loaded downhill situation.